Caster wielding two daggers is able to cast a spell requiring an S component?

@dpnorton Ranger wielding two daggers is able to cast a spell requiring an S component without having to sheathe either weapon first? The ranger would normally need to sheathe one of the daggers, unless the DM or a special ability says otherwise.

@dpnorton Thanks! The focus/component/free hand distinctions are difficult to tease out, and have inspired much confusion. 🙂 The intent: you need a hand free for an S component, unless the spell has an M component and the component/focus is in hand.